Stabilized polyurethane propellants containing aluminum



United States atent 3,266,959 STAEILEZED EGLYURETHANE PROPELLANTS CGNTAINING ALUMHNUM Avery W. Ackley, Orangedaie, Califi, assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy No Drawing. Filed May 5, 1965, Ser. No. 453,902 4 Claims. (Cl. 149-19) This invention relates to a novel solid propellant composition and more particularly to a sustainer propellant with a high specific impulse.

There are several types of solid propellant compositions. One, often called a composite, has two important ingredients, a fuel and an oxidizer, neither of which would burn without the presence of the other; and another type, sometimes called -a homogeneous or doublebase propellant, which contains no crystals, but uses chemically blended oxidizer material to sustain combustion such as a colloid of nitroglycerin and nitrocellulose. Solid propellants have achieved considerable military and civilian importance and improvement of certain characteristics is necessary. A good solid propellant should have a high release of chemical energy, a low molecular Weight of combustion products, high density, low reactivity to atmospheric conditions, high autoignition temperature and good storage qualities. It should be simple, safe and easy to manufacture, handle or transport. The present invention provides a propellant composition having improved specific impulse along with improved chemical and physical properties and bonds well to the rocket motor casing.

It is an object of the present invention to provide a high energy composition possessing properties which adapt it for use as a solid rocket propellant.

Another object is to provide a low burning rate sustainer propellant with higher specific impulse than those available from wholly nitrate-based propellants.

Yet another object is to provide a solid propellant composition which possesses high safety characteristics, with reference to impact sensitivity, autoignition temperature and stability upon storage.

A further object of this invention is to provide a propellant with improved combustion efliciency.

Other objects, features and many of the attendant advantages of this invention will become readily appreciated as the same become better understood by reference to the following detailed description.

Broadly, the invention involves the addition of age stabilizers, a depressant plasticizer and thermite type compositions which improve the age life and combustion efficiency of fuel-rich composite propellant formulations. These formulations comprise generally a mixture of inorganic oxidizers such as ammonium perchlorate and ammonium nitrate, a metal fuel such as aluminum, a burning rate catalyst, a binder consisting essentially of one or more polyurethane monomers, one or more surface active agents such as lecithin and tertiary alkyl amino polyether alcohol, and a polymerization catalyst.

Age stabilizers used in the composition of this invention include antioxidants and squalene. The antioxidant sold under the trade name B-L-E antioxidant was found quite successful. It is an amine reaction product in the form of a non-volatile, amber-colored liquid with a specific gravity of 1.087. Materials exhibiting a thermite type reaction with aluminum and other metals include iron oxide (Fe O antimony trioxide (Sb O chromium trioxide and rare earth oxides. Triactyl phosphate was used as the depressant plasticizer which provides re duction in burning rate.

Patented August 16, 1966 Percent Ingredients y Function weight Ammonium perchlorate 35.00 Oxidizer. Ammonium nitrate 35. Do. Aluminum powder 10. 00 Metal fuel. Ammonium dichromate. 0. 50 Burning rate catalyst. Polypropylene glyc0l 10. 81 Polyurethane monomer. Glycerolmonoricinoleate- 1. 99 Do. Tolylene diisocyanate. 2. 23 Do Trioctyl phOSpllfltG 1. 76 Plasticizer. Ferric acetyl acetonatm 0. Polymerization catalyst. Antioxidant (an amine reaction 0. 25 Age stabilizer.

product). Squalene 2.00 D0. Lecithin- 0. Surface active agent. Trioleate 0. Do. Tertiary alkyl amino polyether 0.10 D0.

alcohol. Dimethyl silicone 0. 01 Antifoam agent.

The anti-oxidant used herein as one of the age stabilizers consists essentially of an amine reaction product in the form of a non-volatile, amber-colored liquid with a specific gravity of 1.087 and is sold under the trade name B-L-E antioxidant. The other age stabilizer is squalene which possesses a structure that contains the skeleton of two farnesol molecules fused head to head. Squalene has the formula Trioleate, sold under the trade name Span 85 was used as one of the surface active agents. It is an oily liquid having a specific gravity of 0.920.98, a flash point F. 500, and a fire point F. 570. Another surface active agent used herein is a tertiary alkyl amino polyether alcohol sold under the trade name Priminox 10. These alcohols have the general formula, RNH(C H O) H. They are liquids that are mostly oil soluble, although some of the members are water soluble. The dimethyl silicone used as an antifoam agent in this formulation is sold as L- Silicone.

The ammonium perchlorate oxidizer is of particle size 10-50 microns and the ammonium nit-rate was about very fine particles (7-20 microns) to obtain minimum burning rates. The aluminum powder ranging in size from 7 to 20 microns gives the most eflicient combustion in the presence of ammonium nitrate. It is necessary to use the optimum particle sizes of oxidizer and fuel to achieve the minimum burning rates.

The following are ballistic parameters for the above formulation:

Mass flow coefiic-ient, c 1b./lb. f.-sec. 0.0066 Ratio of specific heats 1.20

This formulation yields a low burning rate sustainer propellant. It has improved elastomeric properties at reduced temperatures and has improved aging life because of the special stabilizers B-L-E antioxidant and squalene. The propellant bonds well to motor cases or liners and can be used for case bonded dual thrust motors.

The ingredients may be mixed on a roll mill or in an internal mixer such as a Baker-Perkins dispersion blade mixer. The binder ingredients may be blended together first, and the oxidizers and other dry ingredients mixed in stepwise additions. Curing is accomplished at room temperature, but the over-all cure time can be reduced by heating to a temperature in the range of to F The propellant mix may be formed in any desired shape by compression molding, injection molding or extrusion. It may also be poured into the inner cavity of the igniter assembly and cured in place at ordinary temperatures.

In the preparation of the solid rocket propellant composition the percent oxidizer may be varied within the ranges of to 80 percent ammonium perchlorate and 80 to 0 percent ammonium nitrate. The amount of metal may also be varied from 0 to percent. The amount of oxidizer is usually the major amount of the total composition and is generally in the range between 50 to 90 percent by weight of the total propellant composition.

Burning rate catalysts applicable in the invention include ammonium dichromate, iron oxide, antimony sulfide and chromium trioxide in the range of 0 to percent based on the total propellant composition.

Other high energy metal fuel can be used in the propellant composition such as finely divided magnesium and boron. These metals will usually have a particle size within the range of 7'to 30 microns.

Any suitable polyurethane can be used to prepare the propellant compositions of this invention. Presently the polyurethanes are generally those prepared by the interaction of a polyisocyanate with an active hydrogen-containing compound selected from the group consisting of aliphatic saturated and unsaturated polyhydroxy compounds and polyamino compounds containing at least one active hydrogen atom. The polyurethane monomers are usually reacted in substantially stoichiometric amounts.

As will be evident to those skilled in the art various other modifications of the invention can be made, or followed, in view of the above disclosure, without departing from the spirit of scope of the invention.

What is claimed is:

1. A solid propellant composition comprising the following ingredients:

ammonium perchlorate;

ammonium nitrate;

aluminum;

a burning rate catalyst selected from the group consisting of ammonium dichromate, iron oxide, antimony sulfide and chromium trioxide;

a polyurethane binder mixture consisting essentially of polypropylene glycol, glycerolmonoricinoleate, and tolylene diisocyanate;

trioctyl phosphate;

ferric acetyl acetonate;

an antioxidant consisting of an amine reaction product;

squ-alene;

a mixture of surface active agents consisting essentially of lecithin, trioleate, and tertiary alkyl amino polyether alcohol; and dimethyl silicone.

2. A solid propellant composition comprising the following ingredients:

Percent by weight a mixture of ammonium perchlorate and ammonium nitrate in about equal amounts up to 80 a light metal do 10 a burning rate catalyst do 20 a mixture of polyurethane monomers do 22 a plasticizer do 2 a polymerization catalyst do 1 a mixture of age stabilizers do 3 a mixture of surface active agents in about equal amounts up to 1 and an antifoam agent do 0.5

3. A solid propellant composition comprising the following ingredients:

4. A solid propellant composition comprising the following ingredients:

ammonium perchlorate ammonium nitrate aluminum iron oxide polypropylene glycol glycerolmonoricinoleate tolylene diisocyanate trioctyl phosphate ferric acetyl acetonate squalene amine antioxidant lecithin trioleate tertiary alkyl amino polyethylene alcohol dimethyl silicone;

said ammonium perchlorate having a particle size ranging from 10 to 40 microns and said ammonium nitrate having a particle size ranging from 7 to 20 microns; and

said aluminum having a particles size ranging from 7 to 20 microns.

References Cited by the Examiner UNITED STATES PATENTS 3,132,976 5/1964 Klager et al. 14919 References Cited by the Applicant UNITED STATES PATENTS Bice.

Walden. Hudson. Schaefier et al. Cobb et a1.

BENJAMIN R. PADGETT, Acting Primary Examiner. 

1. A SOLID PROPELLANT COMPSOITION COMPRISING THE FOLLOWING INGREDIENTS; AMMONIUM PERCHLORATE AMMONIUM NITRATE; ALUMINUM; A BURING RATE CATALYST SELECTED FROM THE GROUP CONSISTING OF AMMONIUM DICHROMATE, IRON OXIDE, ANTIMONY SULFIDE AND CHROMIUM TIROXIDE; A POLYURETHANE BINDER MIXTURE CONSISTING ESSENTIALLY OF POLYPROPYLENE GLYCOL, GLCEROLMONORICINOLEATE, AND TOLYTENE DIISOCYANATE; TRIOTYL PHOSPHATE; FERRIC ACETYL ACETONATE; AN ANTIOXIDANT CONSISTING OF AN AMINE REACTION PRODUCT; SEQUALENE; A MIXTURE OF SURFACE ACTIVE AGENTS CONSISTING ESSENTIALLY OF LECITHIN, TRIOLEATE, AND TERTIARY ALKYL AMINO POLYETHER ALCOHOL; AND DIMETHYL SILICONE. 